Carrying heavy rucksacks has always usually involved incorrect loading of the back and shoulders. Over the years the development of rucksacks for heavier load bearing has been aimed at reducing the load on the back and shoulders. The founder of Fjällräven raised the rucksack with a carrier frame behind the back in order to displace the centre of gravity towards the body's vertical line and by raising the rucksack the centre of gravity was raised, resulting in a certain degree of instability. The so-called Softpacks with an integrated frame system were aimed at getting the rucksack as close to the body as possible and to displace the centre of gravity to the vertical line of the body and at the same time to keep the centre of gravity down. More of the weight was also able to be distributed down onto the hips with the aid of a waist band so as to reduce the pressure on the back and shoulders. However, a large part of the weight was still borne over the shoulders. The weight on the hips was caused by the rucksack pulling down the waist band from the hips through its connection at the bottom part of the rucksack. The solution does not therefore allow an even distribution of the load around the hip section.
When carrying a rucksack a person had to lean forwards, with the weight over the shoulders, whereby the spine was bent to achieve balance. The weight over the shoulders helps to bend the spine and the spine takes up the occurring moment forces to create balance in the assembly (carrier and rucksack). The back is strained, in particular lower down in the lumbar spine which takes up greater forces during bending of the back.
There are patents for carrier frames with frame structures which are partially at the front of the body for carrying children on the shoulders (for example European Patent Application 81303333.9 from 1981). The main purpose of these carrier frames is to prevent the child from falling off the shoulders. The child sits on the shoulders with support for the child's back and the child's weight is borne on the shoulders without any intention of distributing the weight down to the hips. The sole function of the carrier frame is to prevent the child falling backwards, not to reduce the load on the shoulders.
The problem with current conventional rucksack solutions continues to be painful shoulders and backs with heavy loads over a longer time.
The cause of the problem with the current rucksack solution is a combination of
1. the weight or load relief borne on the shoulders and
2. the forward inclination of the upper body with a bent spine in order to achieve balance
3. the rucksack's pulling behaviour on the soft hip belt resulting in the load relief being concentrated over both iliac crests and not around the entire hip area of the body.
The weight on the shoulders means that it is easier to bend the back forwards in order the carry the rucksack in a balanced manner. In this way a large load is taken up by the shoulders and the lower regions of the back, which results in tiredness or pain in the back, particularly in the lumbar spine which takes up the moment to keep the body in balance.